JP2002531538A - Organic liquid dehydration method - Google Patents

Abstract

  (57) [Summary] The present invention relates to a method for dehydrating an organic liquid mixed with water, said method comprising contacting the mixture with a molecular sieve, pretreating the molecular sieve to reduce its acid site concentration and contacting the mixture with the mixture. Prior to obtaining an ammonia TPD value of 18 μmol / g or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an organic liquid that absorbs water using a pretreated molecular sieve (
In particular, the present invention relates to a method for dehydrating alcohol).

[0002] Alcohols and esters are generally used as reactants in the hydration of olefins to form alcohols or as by-products of the condensation reaction between carboxylic acids and alcohols to form esters, so that water or water-containing environments Generated by In general, the product alcohols or esters are particularly contaminated with water. Furthermore, water is a reactant, especially when an alcohol such as ethanol or isopropanol is produced, for example, by the hydration of an olefin such as ethylene or propylene, respectively, using a synthetic route, so that the product is contaminated with water. Is inevitable. In addition, bio-fermentation routes from agricultural feedstocks such as corn, beet and sugar cane, and for example agricultural residues,
Alcohols produced by the processing of biomass such as herbal crops, waste paper and pulp or municipal waste are also contaminated with water. More importantly, the process of removing water from such materials is complicated by the fact that, for example, in the case of ethanol, its dehydration is difficult by forming an azeotrope with water. A cumbersome and expensive method must be used. Of the various methods suggested for dehydration of hydroalcohols, the following method is considered to be typical: Use of ion exchange resins (DE-
A-4118156); dialysis evaporation using membranes (JP-A-04308543); treatment with a group of catalyst beds following treatment with orthoesters (DD-A-2783).
No. 36); 2 in a catalyst bed comprising an acidic ion exchange resin and an acidic zeolite.
With 2,2-dialkoxypropane (DD-265139); Selective extraction of alcohols in mixtures in liquid carbon dioxide (EP-A-2331072)
Combination of extraction with liquid carbon dioxide with molecular sieves and then use of fractional distillation (EP-A-233 392); azeotropic distillation in the presence of entrainers such as cyclohexane; and, of course, various molecular sieves or zeolites (EP-A-205582, GB-A-2151501, EP
-A-142157, EP-A-158754, US-A-4407662
No., US-A-4372857, GB-A-2088739 and FR-A
-2719039). The use of molecular sieves is an attractive method due to its relative simplicity and low cost. In the last-mentioned FR-A-2719039, the main feature is that the molecular sieve used is regenerated using a superheated partially dried alcohol.

[0003] One of the problems with the use of conventional molecular sieves is, for example, the reversal of the olefin hydration reaction, ie, the secondary conversion of isopropanol to propylene and water or hydrolysis of esters to reactant alcohols and carboxylic acids. Not only are valuable products lost due to the general production of organisms, but also the chemicals, labor and energy initially consumed in the hydration and esterification reactions, respectively.

[0004] It has now been determined that this reversal and consequent loss of purity can be avoided by pretreating the molecular sieve according to the invention prior to contact with the aqueous organic liquid.

Accordingly, the present invention provides a method for dehydrating an organic liquid mixed with water, comprising contacting a mixture with a molecular sieve, wherein the molecular sieve is pretreated to reduce its acid site concentration and prior to contact with the mixture. A method for dehydrating an organic liquid, wherein an ammonia TPD value of 18 μmol / g or less is obtained.

[0006] "Molecular sieve" as used herein means that the sieve itself or such a sieve is bound to or with a binder.

[0007] By "ammonia TPD value" is meant herein the ammonia temperature desorption value, which is the value obtained from molecular sieves after the sieve has been completely saturated with ammonia and then subjected to thermal desorption until no more ammonia is generated. The amount of ammonia desorbed. As described above, the “ammonia TPD value” indicates the concentration of an acid site in a molecular sieve capable of accessing ammonia. Of course, the acid site concentration can be defined by other well-known characterization techniques such as, for example, infrared spectroscopy and microcalorimetry. The ammonia TPD value of the molecular sieve used in the present invention for dehydration is preferably first measured by first pre-weighing a commercial sample of the molecular sieve to an elevated temperature of, for example, about 150 ° C. to about 10 ° C./min.
And then reduce the temperature of the heating sieve to about 100 ° C. over a long period of time (eg, overnight at this temperature) in an inert atmosphere, then reduce the ammonia saturated sieve to 10 ° C./min. Reheat to about 700 ° C at a rate of
It is determined by measuring the amount of ammonia desorbed from the molecular sieve. The measurement of desorbed ammonia can be performed by titration of desorbed gas using a dilute mineral acid solution such as 0.02N hydrochloric acid.

In the case of commercially available molecular sieves of the so-called “potassium cationic type”, ammonia TPD values are generally higher than 19 μmol / g, typically 19
２５25 μmol / g. However, after pretreatment, the treated molecular sieve has an ammonia TPD value of ≦ 18 μmol / g, preferably less than 15 μmol / g,
Preferably it is less than 12 μmol / g, for example 1 to 11.5 μmol / g.

[0009] Molecular sieves capable of adsorbing water from a mixture thereof with alcohols are well known. Typically, this type of molecular sieve is crystalline, but the particular sieve used is not critical. However, such a sieve should be capable of adsorbing at least 2% by weight of water under adsorption conditions, for example 2-30% w / w, preferably about 5-25% w / w. The sieve is preferably a zeolite molecular sieve having an average pore diameter of about 3 Å. A typical example of this type of molecular sieve is type A zeolite (particularly type 3A), but others having different pore diameters, such as 4A and 5A, can also be used. In particular, most commercially available molecular sieves sold as "potassium cationic type" conventionally used in alcohol dehydration processes necessarily have an ammonia TPD value of greater than 19 μmol / g. Typical examples of commercially available zeolite molecular sieves of this type are UOP AS-5078 and SECA Siripolite®
Although sold as NK30, this type of molecular sieve is also available from other sources. Used as such to dehydrate hydroalcohols, these so-called "potassium cationic forms", for example as described in EP-A-0 142 157, contain significant amounts of by-products such as olefins, ethers and / or aldehydes. ). This not only contaminates the by-product treated solvent alcohol, but also adversely affects the quality of the dehydrated alcohol by undergoing further degradation or polymerization in the presence of untreated molecular sieves, resulting in reduced alcohol purity. So unacceptable. Such examples may be found, for example, from column 2, lines 50-60 of US-A-4460476, and from the examples and comparative tests given below.

A feature of the present invention is that this type of so-called “potassium cation type” of zeolite molecular sieve is further processed to determine the ammonia TPD value prior to contact with an organic liquid-water mixture to effect a dehydration process. Is a point that can be reduced to the level of Further processing is preferably carried out by contacting the commercially available molecular sieve with a solution of an ammonium or alkali metal salt (eg a sodium or potassium salt, especially nitrate) to remove residual H ⁺ cations in the commercial sieve with additional alkali metal cation. It is performed by exchanging with ions. A final washing step is then performed to remove any residual salts and acids formed as a result of the ion exchange step. The alkali metal salt is preferably used as an aqueous solution, and the concentration of the aqueous solution of the ammonium salt or alkali metal salt used depends on the nature of the untreated molecular sieve. Typically, however, such concentrations will suitably range from about 0.01 to 2 molar, preferably from about 0.05 to 0.5 molar. The treatment of the untreated molecular sieve is suitably carried out at a temperature in the range from 10 to 90C, preferably from 20 to 70C. In this way, the ammonia TPD value of a commercial molecular sieve, such as 3A, can be reduced to a value of 18 μmol / g, or suitably less than 15 μmol / g, preferably less than 12 μmol / g. Generally, the ammonia TPD value of the untreated molecular sieve is reduced by at least 10%, preferably by at least 40%, before use in the dewatering method of the present invention. Alternatively, the above treatment can be performed with any binder used in making the bound molecular sieve prior to binding the sieve to or to the binder. In this case, the treatment is the ammonia T of the final combined molecular sieve.
It should be performed to such an extent that the PD value falls within the above specific range. Typical binders used in bonded molecular sieves are montmorillonite, kaolin, sepiolite and attapulgite.

In the dehydration process, a molecular sieve having a reduced ammonia TPD value is contacted with the organic liquid-water mixture to be dehydrated. This can be done batchwise or continuously, for example, by packing a column with a predetermined amount of a substantially acid-free molecular sieve and then passing the mixture to be dewatered through. The rate of passage of the mixture to be dehydrated through the packed column is such that there is sufficient contact time between the mixture and the sieve. Of course, this kind of contact time depends on:
a. Nature of the organic liquid in the mixture b. Amount of water in the mixture c. Molecular sieve capacity used d. Temperature and pressure at which the two are brought into contact e. Whether the mixture is liquid or gaseous

Typically, however, such contact times are preferably in the range from 15 seconds to 5 minutes per unit volume of the mixture passing through the unit volume of the molecular sieve. If, within this range, the mixture is, for example, a liquid mixture of water and isopropanol and passes through a pretreated crystalline 3A molecular sieve at a temperature of about 110-120 ° C., such a contact time can be about 30 seconds to 3 minutes. Range, for example about 1 minute per unit volume of the mixture passing through the unit volume of the treated molecular sieve. By operating this method, a substantially water-free organic liquid can be recovered from the bottom of the column, assuming that the mixture to be dehydrated is being fed to the top of the packed column.

[0013] Depending on the efficiency of the molecular sieve, the water-saturable used sieve can be regenerated by temperature swing desorption or pressure swing desorption techniques, ie it can desorb adsorbed water. In the temperature swing method, a flow of a thermal fluid is passed through a molecular sieve to be used, and adsorbed water is pushed out of the sieve. For a given pressure,
The amount of adsorbed water decreases with increasing temperature. In the pressure swing method, desorption of adsorbed water can be achieved by significantly reducing the pressure as compared to the pressure at which the adsorption was performed.

[0014] The efficiency of the dehydration method can be improved by operating two columns simultaneously, so that when one of the columns is in the adsorption mode, the other is in the desorption mode to adsorb the feed of the mixture to be treated. Passing the column in mode allows for substantially continuous operation.

[0015] The process comprises alcohols such as, for example, ethanol, isopropanol, secondary butanol and tertiary butanol, and aliphatic esters such as, for example, n-propyl formate, ethyl acetate, butyl acetate, methyl propionate and ethyl isobutyrate. When dewatering, they may be produced by synthetic routes, such as, for example, alcohols produced by the olefin hydration process, or they may be produced by biofermentation of agricultural feedstocks, such as, for example, corn, beet and molasses Particularly suitable for use depending on whether or not the biofermentation process is used, for example, alcohols produced by the treatment of biomass such as agricultural residues, herbal crops, waste paper and pulp, and municipal solid waste, especially ethanol / water Contains mixtures.

Hereinafter, the present invention will be further described with reference to examples and comparative tests (not according to the present invention).

[0017]Example:  In the examples and comparative tests, two commercial grades of potassium ion exchange
VuraSieve (Zeolite 3A), ie, UOP AS-5078 (Universa)
Le Oil Products Co., Ltd.) and SECA Siripolite (registered trademark) NK30 (
SECA), both of which are sieves already bound to the binder.

A.Processing of molecular sieves  The following procedures are used to add these commercially available molecular sieves to additional
Treatment with potassium metal salts reduced the acidity of these commercial samples.

Potassium nitrate (2.05 g, Sigma-Aldrich) was added to distilled water (20 ml).
To prepare an aqueous solution of potassium nitrate (0.1 M). The obtained potassium nitrate solution was poured into a container to retain zeolite 3A molecular sieve (75 g). The vessel was sealed and stirred periodically at room temperature for 20 hours. The obtained potassium ion exchange molecular sieve was filtered, washed with distilled water (200 ml each) three times, and dried at 140 ° C. in an oven. The potassium ion exchange molecular sieves were then crushed and sieved to an average particle size of about 0.5-0.85 mm for use in a dehydration test rig.

B.Ammonia temperature programmed desorption experiment:  Precisely place untreated commercial molecular sieve sample (300 mg) in quartz U-tube
Weighed in and attached to ammonia TPD device. Sample at a rate of 10 ° C per minute
The mixture was heated to 150 ° C under flowing nitrogen and kept at 150 ° C for 1 hour. Then
The temperature was reduced to 100 ° C. and the sample was annealed with 1% ammonia in a nitrogen stream.
Saturated with Monia. After flushing with nitrogen at 100 ° C. overnight, the sample was
Heated to 700 ° C at a rate of 10 ° C. Desorbed ammonia with 0.02N hydrochloric acid
It was continuously titrated.

[0021] UOP AS-5075 and SECA Siripolite® NK, respectively
One fresh sample of each of the -30 sieves was subjected to a potassium ion exchange procedure (summarized in Section A above). Each sample was then similarly separately subjected to two further exchanges with potassium ions to obtain "triple exchange" sieves.

The total amount of ammonia desorbed from each of the fresh and “triple-exchange” sieves is shown in Table 1 below. The triple exchange sieve had an ammonia adsorption capacity of only 55% of the fresh (untreated) UOP sample and only 48% of the fresh (untreated) SECA sample.

[0023]

[Table 1]

C.Dehydration test (A): isopropanol  The dehydration test was performed as follows: 30 ml potassium ion exchange from step (A)
The adsorption bed consisting of the modified molecular sieve is packed in a glass reactor and then inert
Fill 5 ml of fused alumina beads for use as a heater floor,
Separated from the bed by a quantity of glass wool.

With the filled glass reactor fixed in place, a flowing nitrogen flow (50 ml / m
heated to 300 ° C. under in) for 16 hours. The adsorbent bed is then heated to 120 ° C.
And the nitrogen flow rate was reduced to 25 ml / min. A model azeotropic isopropanol mixture containing 88% w / w isopropanol and 12% w / w distilled water was flowed through the bed at a liquid flow rate of 2 ml / hr. A collection vessel (maintained at room temperature) was positioned downstream of the reactor to collect the dehydrated (dry) liquid. The gas sample point was located downstream of the collection vessel. The gas flowing downstream from the collection vessel was analyzed at regular intervals using a gas chromatogram equipped with an alumina KCI PLOT capillary column. Decomposition of isopropanol as it flows over the potassium ion exchange molecular sieve is indicated by the presence of propylene in the outlet gas stream downstream of the collection vessel. Liquid samples were collected, weighed, and analyzed using a gas chromatogram fitted with a Propack® S packed column. Analysis of the collected liquid sample indicated that the water was selectively adsorbed. GC analysis is no longer
No other detectable product was shown in the condensed liquid sample. These tests were stopped before water breaks against the bed.

The results of the molecular sieves tested in both forms, fresh (commercial (not according to the invention)) and after potassium ion exchange according to the invention, are shown in the following table (Table 2):

[Table 2]

The above results clearly show that the decomposition of isopropanol to propylene upon dehydration on commercially available molecular sieves is dramatically reduced when the sieves have been subjected to a prior potassium ion exchange treatment.

[0028](B): ethanol  The dehydration test was performed as follows: 30 ml UOP AS-5078 molecular
Potassium ion exchange treatment using a sieve or the route described in the above step (A).
An adsorbent bed of the same sieve after packing is charged to a glass reactor and then inert
Packed with 15 ml of fused alumina beads for use as a heater bed
Separated from the bed by a small amount of glass wool.

The filled glass reactor was fixed in place and heated to 350 ° C. for 16 hours under flowing nitrogen flow (50 ml / min). The bed was then cooled to 155 ° C. and the nitrogen flow was reduced to 10 ml / min. A model azeotropic ethanol mixture containing 94.4% w / w ethanol and 5.6% w / w distilled water was added to 2 m
The liquid was passed through the adsorption bed at a liquid flow rate of 1 / hr. A collection vessel (cooled using an ice bath) was positioned downstream of the reactor to collect the dehydrated (dry) liquid. The collected liquid samples were weighed and analyzed for diethyl ether using a gas chromatogram fitted with a CP wax-57CB capillary column. Karl Fischer titration analysis of the collected liquid sample indicated that water had been adsorbed. The test was stopped before the water broke from the bed.

The results of the molecular sieves tested for both forms, fresh fresh (not according to the invention) and after potassium ion exchange treatment according to the invention, are given in the table below (Table 3).
Shown in:

[Table 3]

As the above results clearly show, the formation of diethyl ether during dehydration on commercially available molecular sieves is dramatically reduced when the sieves have been subjected to a prior potassium ion exchange treatment.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] September 14, 2000 (2000.9.14)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 20/28 B01J 20/28 Z 20/32 20/32 20/34 20/34 EH C01B 39/00 C01B 39/00 39/18 39/18 C07C 31/08 C07C 31/08 31/10 31/10 31/12 31/12 (31) Priority claim number 9906298.6 (32) Priority date March 1999 (18) March 18, 1999 (33) Priority country United Kingdom (GB) (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE , IT, LU, MC, NL, PT, SE), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP ( GH, GM, KE, LS, MW, SD, SL, Z, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IN, IS, JP, KE , KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Aldroid, Richard, Duncan United Kingdom Country, T92 Udub, Kent, Tonbridge Hill Top 78 (72) Inventor Smith, Warren, John T. D.B., 134 England, Middlesex, Feltham, Hanover Avenue 89 F-term (reference) 4D017 AA03 AA06 BA01 CA05 CB01 DA01 4G066 AA61B AA62B AA63D AA64D BA23 BA36 BA38 CA43 DA10 FA11 FA28 FA34 FA37 GA14 GA16 4G073 CM05 CM06 CM09 CM15 CZ02 CZ03 FA14 FB29 UB38 4H006 AA02 AD17 BC51 FE11

Claims (20)

[Claims] 1. A method for dehydrating an organic liquid mixed with water, comprising contacting a mixture with a molecular sieve, wherein the molecular sieve is pretreated to reduce its acid site concentration and to have a concentration of 18 micromoles prior to contact with the mixture. A method for dehydrating an organic liquid, wherein an ammonia TPD value of / g or less is obtained. 2. The method according to claim 1, wherein the molecular sieve is pretreated to reduce its acid site concentration and to obtain an ammonia TPD value of 1 to 11.5 micromol / g. 3. The method according to claim 1, wherein the molecular sieve is a zeolite molecular sieve having an average pore diameter of about 3 Å. 4. The molecular sieve of claim 1, wherein said molecular sieve is of the potassium cation type.
The method according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the pretreatment is performed by contacting the molecular sieve with a solution of an ammonium salt or an alkali metal salt. 6. The method according to claim 5, wherein said solution is a solution of sodium nitrate or potassium nitrate. 7. The method according to claim 5, wherein the solution has a concentration of 0.01 to 2 molar. 8. The method according to claim 1, wherein the pretreatment is performed at a temperature of 10 to 90 ° C. 9. The method according to claim 1, wherein the pretreatment reduces the molecular sieve TPD value by at least 4.
9. The method according to any one of claims 1 to 8, wherein the method is reduced by 0%. 10. The method according to claim 1, wherein the molecular sieve is bound with a binder.
10. The method according to any one of claims 9 to 9. 11. The method according to claim 10, wherein said binder is formed of montmorillonite, kaolin, sepiolite or attapulgite. 12. The method according to claim 1, wherein after said pretreatment step, a column is filled with a predetermined amount of said pretreatment molecular sieve, and said mixture is then passed through said mixture to bring said mixture into contact with said pretreatment molecular sieve. The method according to any one of the preceding claims. 13. Mixing the mixture with pretreated molecular sieves
The method according to claim 12, wherein the contacting is performed at a temperature of ° C. 14. The method of any one of claims 1 to 13, further comprising the step of regenerating the molecular sieve after contacting said molecular sieve with said mixture. 15. The method according to claim 14, wherein the regeneration step is performed by temperature swing desorption or pressure swing desorption. 16. The method according to claim 1, wherein the organic liquid comprises an alcohol. 17. The method of claim 16, wherein said alcohol is selected from the group consisting of ethanol, isopropanol, secondary butanol and tertiary butanol. 18. The method according to claim 1, wherein the organic liquid comprises an ester. 19. The method of claim 1, wherein said ester is selected from the group consisting of n-propyl formate, ethyl acetate, butyl acetate, methyl propionate and ethyl isobutyrate.
9. The method according to 8. 20. A method of treating a molecular sieve, comprising treating the molecular sieve to reduce its acid site concentration and obtaining an ammonia TPD value of 18 micromol / g.